This invention relates to a low ratio yarn package treatment apparatus and method. Most modem yarn dyeing is carried out after the yarn has been wound onto suitable packages and formed into cheeses, cones or cakes, which are then mounted onto perforated spindles carried on a yarn package carrier. The loaded carrier is then placed into a pressure vessel, and the yarn is dyed by forcing a liquor of water, dye and perhaps various additives through the packages. Early machines were open to the atmosphere and dyeing took place only from the inside to the outside of the package, i.e., the dye liquor was forced from the perforated spindles through the yarn from the inside of the package to the outside. The liquor was then withdrawn from the vessel and recirculated in the same manner.
Later machines were enclosed, and by reversing a liquor pump, liquor could be alternately forced through the yarn from the inside to the outside and then from the outside to the inside. This process remains the most commonly used, because the alternating inside-out, outside-in dyeing results in the most uniform dyeing of the yarn.
In conventional package dyeing machines, the liquor ratio is relatively constant and is based on the weight of the yarn which can be dyed in a given capacity vessel. The "ratio" is based on the weight of yarn that can be dyed using a given weight of liquor. Thus, a ratio of 10:1 refers to a dye process where, for example, 10,000 pounds of liquor is required to dye 1,000 pounds of yarn. This normally occurs when the vessel is fully flooded, completely covering the yarn package carrier and filling even the domed cover of the vessel.
While this practice generally provides the best dyeing results, particularly with deep shades, this large ratio results in a considerable amount of dye being left over in the liquor after dyeing is complete. The dye is typically dumped with the waste water into a nearby river or sewer, or into a wastewater holding area or treatment facility. Increasingly strict government regulation in many areas now limits the extent to which wastewater containing dyes and other yarn treatment additives can be disposed of without expensive treatment processes.
These requirements, as well as demands for energy conservation, reduced dyeing costs and faster dyeing times have led to techniques whereby varying amounts of dye liquor are used in order to reduce the liquor ratio. One such technique involves partially flooding the vessel to above the level of the packages, but leaving the dome of the vessel unfilled, thus reducing the liquor ratio to about 8:1. Another technique involves a low-liquor state in which only the base of the carrier is covered with dye liquor. The liquor is pumped up through the spindles of the carrier and through the packages from the inside-out. Liquor ratios can be reduced to 4:1 or even 3:1 using this technique. However, dyeing can take place only in the in-to-out flow direction. The packages must be sufficiently rigid not to distort under these conditions. Significant economies can be obtained by reducing the liquor ratio in this manner. However, the economies obtained are often outweighed by difficulties with dye solubility, dispersion stability and dyeing unevenness, particularly where deep shades are being imparted to the yarn.
The present invention achieves low ratio dyeing on the order of 4:1 or 3:1 while nevertheless permitting full submersion of the yarn packages and alternating in-to-out and out-to-in dyeing. This is accomplished while otherwise carrying out conventional dyeing processes using conventional dyes and additives, and with equipment which can be modified from conventional dyeing equipment.
While dyeing is described in this application as a preferred embodiment of the practice of the method of the invention, the invention is intended to apply to all types of yarn treatments wherein yarn is wet-processed in a dye vessel. It is believed that the invention may have broad application to the dyeing of fibers in the form of raw stock, various yarn forms and even in apparel form, consistent with the principles set out in this application.